Two-step sedimentation process for selection of microcapsules containing cell aggregates.

Area of Science:

• Biomaterials Science
• Cell Encapsulation Technology
• Transplantation Immunology

Background:

• Microencapsulation aims to protect transplanted islets, reducing immunosuppression needs.
• Challenges include immune rejection of unencapsulated cells and increased transplant volume from empty beads.
• Effective separation of encapsulated cells from byproducts is crucial for successful islet transplantation.

Purpose of the Study:

• To investigate density-based separation processes for removing byproducts from microencapsulated islets.
• To optimize separation methods for enhancing the purity of cell-containing alginate beads.
• To improve the efficiency and safety of islet transplantation through byproduct removal.

Main Methods:

• Determined densities of mouse insulinoma 6 (MIN6) cell aggregates (~1.065 g/ml) and empty alginate beads (~1.042 g/ml).
• Employed sedimentation under unit gravity in continuous polysucrose and sodium diatrizoate gradients (density ranges 1.032-1.045 g/ml).
• Utilized centrifugation in a 1.055 g/ml density solution to separate remaining unencapsulated aggregates.

Main Results:

• A polysucrose gradient of 1.039-1.042 g/ml achieved ~80% recovery of aggregate-containing beads, superior to other gradients (~60%).
• The optimized gradient yielded purified beads with only ~6% of their volume occupied by cell aggregates.
• Subsequent centrifugation effectively separated residual unencapsulated aggregates from the purified bead fraction.

Conclusions:

• Sedimentation-based separation effectively removes empty beads and unencapsulated cells from microencapsulated islet preparations.
• Optimized density gradients significantly improve the purity of cell-containing beads for transplantation.
• These methods enhance the potential for successful islet transplantation by minimizing immune rejection and transplant volume.